Page 1 - How to Flare Tube Guide

Inline Tube - Tips For A Perfect Flare

What should I use 45 or 37 degree flares
There are many different plumbing systems available, and which one is right for your application? We are going to
talk about the 3 most common: Inverted Flare, -AN and Pipe.

Inverted Flare or 45 is on all standard automotive applications, cars and trucks from the 30's to mid 80's have
inverted flare fittings at all the connections. Inverted flare is a single nut that uses a 45 degree double flare. This flare
is lapped over so the tube is double thickness at the end. A inverted or double flare has a tube nut that pushes the
flare against the brass seat to make a leak proof connection. For a leak to stop the flare it must seal against the brass
seat. Using Teflon tape does no good because the thread is not what seals the line to the flare. The tape seals the
thread but the fluid will still leak between the tube and the hole in the fitting. When sealing newly flared lines to old
components the line must be tightened then loosened and the process must be repeated until the leak stops. If
component brass seat is used, you are trying to seat over the existing crush ring, this may take a few tries but
repeating the process will form the line flare to the brass seat. To form the end of the tube it requires a 45 degree
double flare tool. Inverted flare fittings and tools are always less expensive because they are more common.

-AN or 37 is short for army/navy standard this system was never used on new cars from the factory. The -AN system
was used on military equipment and introduced into the auto aftermarket in the 60's. The -AN fittings are a two part
fitting part, one is a nut and part two is a sleeve. The nut holds the sleeve and tube in place. Since -AN uses a 37
degree single flare a sleeve is required to give extra support to the flare. This single flare can leave a rough edge to
the tube since it is not rolled over. Since -AN fittings were never used on factory applications a adapter fitting must be
used on any factory master cylinder or proportioning valve. So instead of having one fitting into the master when
using inverted flare there will now be a nut, sleeve, and adapter. The down side is that there are now three
connections and the cost of three fittings. To form the end of the tube it requires a 37 degree single flare tool. -AN
flare fittings and tools are generally more expensive because they are less common.

Pipe is a tapered thread that uses the thread of the fitting to seal against the thread wall of the component. Teflon
tape is used at this connection because the threads are sealing the part. All tapered fittings are pipe and require tape.
Pipe fittings can also be seen on factory cars, some fuel pumps, and other components use pipe thread. Most after
market parts: residual valves, adjustable valves, aftermarket calipers, thru frame fittings, and etc are made using pipe
thread. Pipe thread is a universal system designed to work with all systems. Pipe thread is used to connect different
systems. Pipe adapters are made for both -AN and inverted flare.

The problem with all these systems is it's like different languages and -AN is one language, inverted flare is another
language, and pipe is the translator. Pipe works with both but -AN and Inverted flare do not work together.

If you choose to use -AN you will have a 37 degree flare and if you choose Inverted flare you will have a 45 degree
double flare. The double flare is a stronger flare but more difficult to make. Both of these flares can be formed on
stainless as well as tin steel tube. Knowledge and practice make a perfect flare. We have outlined the steps in the
process for both tools. By following these steps you will achieve a perfect flare every time.

Use the right tube
Not all tubing is the same, there are many grades and thickness. This makes the difference in being able to flare the
tube. Automotive tubing is .028 wall thick. Thicker tubes .035 and .048 are a nightmare to bend because they are
thicker. The thicker tube also reduces the inside diameter so your brake fluid flow is restricted.
Steel Tube: has a tin coating for corrosion resistance. The heating process of the tubing for the coating causes the
tube to be hard or soft. Also depending on what the tubing is made for it can be single wall or double wall tube. On
single wall tube the weld seam is clearly visible and this tube will be cheaper and much harder to work with (Not
worth it). Double wall tube is much softer and there is no seam. Some steel tube has no coating and while it saves
money it will rust almost right away. Inline Tube uses the best tube on the market, it is doubled wall with a tin coating
on the outside and a copper coating on the inside made to automotive specifications to be effortless to end form and
bend. Tubing has many uses and general tube from the supply house has general specifications. Inline Tubing is

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